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By A. T. Aldred, K. M. Myles

The vapor pressure of chromium over solid V-Cr alloys has been measured by the torsion-effusion method in the temperature range 1450" to 1650°K. The chemical activities as well as the free energies, entropies, and enthalpies of formation of the alloys have hem computed from the vapor-pressure data. The activities of both chromium and vanadium exhibit fairly small negative deviations from Raoult's law over the entire composition range. The values of the excess entropies and the enthalpies of formation found at 1550°K are considered in terms of the changes in the clzaracteristic properties of vanadium and chromium that occur upon alloying. RECENT interest in the theory and properties of transition-metal alloys has shown the need for relevant thermodynamic data. The present investigation of the V-Cr system was undertaken as part of a more general study of thermodynamic properties of transition-metal alloys. The system was chosen because of the reported complete solid solubility of the components at all temperatures1 and because the difference in magnitude of the vapor pressures of vanadium and chromium allowed a simple effusion technique to be used. The torsion-effusion method was employed to minimize compositional changes in the alloys during the experiments. EXPERIMENTAL Equipment. The torsion-effusion apparatus, shown diagrammatic ally in Fig. 1, consists of a torsion system suspended inside a vertical vacuum chamber whose lower end is surrounded by a high-temperature vacuum furnace. An auxiliary optical lever and screen are used to determine the angle of rotation of the effusion cell. The torsion fiber is an annealed, high-purity, tungsten wire usually between 0.003 and 0.007 cm in diameter and about 43 cm long. The wire supports a concave mirror and a rigid tantalum connector tube. The effusion cell is fastened to the lower end of the connector tube by a dovetailed yoke and har- ness arrangement. The cells, which are 1.27 cm in diameter and 4.4 cm long, were made by electron-beam welding tantalum endcaps onto a 0.025-cm-wall tantalum tube. The two orifices, formed by drilling, have similar areas ranging from 0.011 to 0.031 sq cm. The noninductive sheath-type furnace consists of a single-phase tantalum heating element 6.35 cm in diameter, 15 cm high, and 0.013 cm thick; the element is completely surrounded by radiation shields in an evacuated chamber. The power system includes a 17-kva self-saturating saturable core reactor with an integral magnetic amplifier and a water-cooled, 15-kva, step-down power transformer with a multitap secondary. Temperatures are controlled to within ±1/2o at 1600°K by means of a unit that includes a reference voltage source, a dc electronic null detector, a current-adjusting proportional band relay, and the self - saturating reactor. At 1650°K the temperature variation within the cell, vertically and horizontally, is 3/4oK. Unwanted motions of the torsion system are damped by the movement of an aluminum vane, which is mounted on the connector tube, between the poles of an electromagnet. When not in use the magnet is withdrawn and rotated 90 deg to prevent its interaction with the rotation of the system. Measurements. The vapor pressure, p, is re-

Jan 1, 1964

pAbad, Leopoldo F., Min, Engr,, Div. of Mines, Bureau of Science Manila, P. 1. '23 Abadilla, Quirico A,, Geol., Lago Pet. Corp Box 172, Maracaibo, Venezuela, '20 Abbey, Robert Graham, The W. W. Sly Mfg, Co Train Ave., Cleveland, Ohio. '21 Abbott, A. N., Mines Supt., Mazapil Copper Co., Ltd Concepcion del Oro, Mexico, '28 Abbott, Clarence E., Mgr., Mines & Quarries, Tenn, Coal, Iron & R. R, Co,, 1242 Brown Marx Bldg,, Birmingham, Ala. '04]

Jan 1, 1928

By Albert Sauveur

THE senior author of this paper has expressed the belief that when gamma iron transforms into alpha iron on reaching the A3 point, each gamma grain does not change bodily into one or more alpha grains but that the alpha phase forms first at the boundaries and along the crystallographic planes of the austenite grains.1 To quote: On cooling through the point A, at about 900° C., iron passes from the gamma condition to a. new allotropic form generally designated as alpha. This transforma¬tion, however, is not instantaneous. There are good reasons for believing that it begins at the grain boundaries and along the octahedral planes of the crystals and that it progresses until each grain of gamma iron is changed into a grain of alpha iron, the resulting structure being similar to that of gamma iron. Were it possible to retain at room temperature pure iron but partially transformed, it seems probable that a Widmanstättian structure, or rather, as later explained, a martensitic structure would be observed (Fig. 1), consisting of alpha iron at the boundaries and at the octahedral planes, and of a groundmass of gamma iron. In order to confirm, if possible, the accuracy of that view, a number of experiments were conducted. Polished samples of electrolytic iron were heated in a vacuum, maintained in the gamma range for several hours and quenched in different media. It was hoped by such means to produce and retain on the polished surfaces a pattern which would reveal the mechanism of the allotropic transformation. The samples were placed in evacuated quartz tubes, heated to 1000° C. and held 2 hr. at that temperature. The tubes were then immersed in the quenching bath. Iced brine and liquid air were used first. The polyhedral austenitic structure existing at the time of immersion was very clearly revealed (Fig. 2). This is generally ascribed to iron volatilizing at the grain boundaries.

Jan 1, 1929

By D. W. Gentry, H. E. Sherer

Determining the age at which to replace a specific piece of mining equipment, and choice of the best possible replacement, is a problem common to nearly all mining operations. This paper examines the data required for intelligent equipment replacement decisions and discusses how to predict future repair cost from historic data, determine the total cost of various replacement alternatives, and evaluate the different replacement alternatives. Various operations research and computer methods were used to develop this easily-used, practical equipment replacement method.

Jan 1, 1984

THOSE NOT MARKED ARE MEMBERS; MARKED THUS t ARE ASSOCIATES. HEAVY-FACED TYPE SIGNIFIES HONORARY MEMBERSHIP. JUNIOR MEMBERS ARE MARKED II. THE FIGURES AT THE END OF THE ADDRESS INDICATE THE YEAR OF ELECTION. AARONS, J. BOYD, Genl. Mgr., Chaffers G. M. Co., Boulder City, West. Australia. '05 ABADIE, EMILE R., Min. Engr Box 291, Porterville, Tulare Co., Cal. '76 ABBOTT, CLARENCE E., Genl. Supt., Iron Mines Div., 1405 Minnesota Ave., Bessemer, Ala. '04 ABBOTT, J. W., Min. Engr., "St. Omer," 123 N. Grand Ave., Los Angeles, Cal. '94 ABBOTT, Louis BENJAMIN, Chief Engr., Consolidation Coal Co., Elkhorn Div., Jenkins, Ky. '15 ABBOTT, ROBERT R., Met. Engr., Peerless Motor Car Co., Cleveland, Ohio. '12 ABE, ASAKA Yamagano G. M., Satsuma-Gori, Satsuma, Japan. '14 || ABRAHAMS, A. I., Student 1391 Madison Ave., New York, N. Y. '14 tACKER, E. O'C., Met Bethlehem Steel Co., Bethlehem, Pa. '86 ACKER, Louis K., JR., Min. Engr 565 Highland Place, Bellevue, Pa. '08 ADACHI, JINZOO 11 Shiba Park, Shiba-ku, Tokyo, Japan. '88 ADAMI, C. J., Min. Engr., St. Joseph and Doe Run Lead Companies, Bonne Terre, Mo. '12

Jan 1, 1917

By C. Norman Cochran

The pllnse diagvam for the NaF-AlF3 system was used to calcutate an ionic model for the NaF-AlF3 system. Assuming an ideal solution,a series of simultaneous equations expressing equilibria be-tween solid and liquid phases at the euleclic, perilec-tic, and melting points were solved for the activities of the ionic species, the dissociation constants, and the entropies and heats of fusion. The calculations suggest the existence of A13F1415 ions in addition to the F-1+AlF6-3 , and AlF4-4 ions previously proposed by others. The calculaled valnes give better agreement with vapor pressures than the previous model without Al3Fl14-5. Additional possible vefinements of the model are proposed. CRYOSCOPIC1 investigations and density data2 for the NaF-A1F3 system have previously been used to study the dissociation mechanism of Na3A1F6 and to derive equilibrium constants for its dissociation to NaF and NaAlF,. Depending primarily on the heat of fusion assumed for cryolite, the dissociation constants ranged between 0.02 and 0.18 from cryoscopic studies, and from 0.09 at 1273°K to 0.16 at 1363°K from density data. In most cases the values were unable to reproduce satisfactorily the experimental liquidus lines very far on the A1F3 side of the Na3A1Fe composition. This suggested the existence of at least one other ionized compound in the melt besides NaA1F4 in the Na3A1F6-A1F3 side of the system. This is assumed to be liquid Na&13F14 (chiolite), which is already established as a stable solid in phase studies of this system. MODEL FOR THE MELT The melt is assumed to be an ideal solution with ion activities equal to anion fractions. The only cation in the model is sodium so that Temkin and simple anionic activities are identical. Although the compounds are completely ionized to Na' and the respective anion in the melt, molecular rather than ionic notation is used throughout this work. The Na3A1Fe is assumed to dissociate to NaA1F4 and NaF as in the former model, and Na&13F14 to dissociate to Na3A1Fe and NaA1F4. Other valid dissociation equilibria can be written involving these four compounds, but all of these can be obtained by combinations of the two described dissociation reactions and, thus, are automatically considered in these calculations. The model allows for no free AlF3 so that compositions for NAIF3 > 0.5 (mole fraction A1F3 on the NaF-A1F3 basis) cannot be treated. The question of the existence of free AlF3 in the melt will be discussed again later. The constants in the model were evaluated from points along the entire known liquidus line of the NaF-A1F3 system. Previous work employed only the liquidus line or densi- ties near the Na3A1F, composition. The liquidus line compositions used in the solution of the model are from unpublished work by Mr. P. A. Foster, Jr., for compositions between the Na3A1F6 melting point and the Na&13F14-A1F3 eutectic, and from the published works of Grjotheim,1 Phillips,3 and Foster4 for the remainder of the system. The relationships used in solving for the desired dissociation constants and heats and entropies of fusion are listed in Table I, and the points along the liquidus line at which each apply are indicated to the right of the relationships. The mole fractions of each of the separate species in the melt are symbolized by N. Relationships [I] and [2] are the respective dissocia-ation constants, Kl and K2, of Na3AIF6 and Na5A13F14 for this model. For simplicity, these constants will be assumed to be independent of temperature. Relationship [3] follows from the assumption of the ideal solution. The expression relating the values of N to the experimental values of NAIf3, is given in Relationship (41. Relationships [5], [6], and [7] each state the equilibrium between a compound in the melt and its pure solid phase for the portion of the liquidus lines where it precipitates. The heats of melting, AH,, and entropies of melting, AS,, used in [5], [6], and [7] are assumed to be independent of temperature. The compositions and temperatures of all five invariant points (two melting points, two eutectics, and one peritectic) along the liquidus lines from NAIF3 = 0 to NAIF3 = 0.5 were employed in the solution. The eutectic and peritectic compositions were particularly useful because each of these is involved in one more equation than other points along the liquidus lines and thus reduces the number of points required to solve for the constants. Also, their use assures that the inflection points in the derived liquidus line will correspond exactly with those on the experimental liquidus line. The total number of equations is 5k1 — 1, where n is the number of experimental composition points used. The number of unknowns is 4n + 5 (4n- 3 values of N, 3 values each of AH, and AS,, and 2 values of K). Thus, six points must be used in the solution to obtain an equal number of equations and unknowns. The one additional required experimental composition was taken on the liquidus line between the Na3A1Fe melting point and the Na3A1F6-Na5A13F14 peritectic. Previous work indicated this was a difficult portion of the curve to fit. The temperature used for the point was 1161°K, the same as for the NaF-Na3A1Fe eutectic. This choice of temperature gave two points with identical NNa3AIF6 values which simplifies the algebraic solution. The second point at this temperature is denoted 1161°'K. PROCEDURE FOR SOLUTION OF EQUATIONS Values were assumed for NNa,AIF and NNaF at the NaF-Na3A1F6 eutectic at 1161°k. By an iterative procedure, the corresponding values for NNa5A13F14 and NNaAlF4 at 1161°K were determined from 131 and 141. A value was assumed for NNaAlF4 at 1161°'K and

Jan 1, 1968

By T. D. Yensen

It is safe to say that of all the different materials that go to make up electrical machinery, iron is the most important. Upon its magnetic and electrical quality depends not only the efficiency of the machine but, to a very large extent, the cost. Aside from the mechanical strength, there are three characteristics of iron that are of importance in this connection, viz., magnetic hysteresis, electrical resistance, and magnetic permeability. In the homopolar machine, where the magnetic flux is unidirectional, permeability is the only important factor, but in all other machines the flux is reversed in one or more parts and causes losses due to hysteresis and eddy currents. The eddy-current loss depends largely upon the electrical resistance of the iron; the higher the resistance the lower the loss, under otherwise identical conditions. These hysteresis and eddy-current losses cause heating of the machine, and as they depend upon the magnetic density in the iron, this density must be regulated so that the heating shall not be excessive. If the hysteresis and eddy-current losses and the permeability of the magnetic circuit will permit an increase in the magnetic density, or, in other words, a decrease in the amount of iron, this in turn will mean a decrease in the amount of copper needed, with a consequent decrease in the copper loss. It is thus seen that, indirectly as well as directly, the above characteristics have an important bearing on both the efficiency and the cost of electrical machinery. In general, it may be said that iron for electrical machinery should have the following characteristics: (1) low hysteresis loss, (2) high electrical resistance, and (3) high permeability. These are the characteristics that investigators have been striving to attain since electrical machinery first came into use. Until the beginning of the present century, Swedish charcoal iron was regarded as the best grade of iron for magnetic purposes, and even now it ranks high among the various grades used. About that time Sir Robert Hadfield1 produced a number of iron alloys that revolution-

Jan 1, 1916

By R. T. Hukki

This paper presents a series of equations for mechanical ball wear, relating parameters of ball size, mill speed, and mill diameter. The fundamental equation, Eq. 12, presented here is introduced to correlate these basic parameters and thus define and clarify the concept of ball wear. This equation is offered as a general rule, which may be modified to apply to individual problems of grinding. BALL wear as observed in grinding installations is the combined result of mechanical wear and corrosion. Corrosion should be a linear function of the ball surface available. Ball corrosion, however, has been studied so little that its effect, although of great importance, cannot be included in the analyses given here. In a separate paper' it is shown that 1 n = 0.7663 np----=— rpm [1] vD P = c, np D kw [2] T=c²(np)n De tph [3] In these equations n — actual mill speed, rpm np = calculated percentage critical speed D = ID of mill in feet P = power required to operate a mill, kw T = capacity of a mill, tph C¹ and c² - appropriate constants in = exponent of numerical value of 1 5 m 1.5 Exponent m is the slope of a straight line on logarithmic paper relating mill speed (on the abscissa) and mill capacity (on the ordinate). It is generally accepted, although not sharply defined, that ball wear in mills running at low (cascading) speeds is a function of the ball surface available. Accordingly, the wear of a single ball may be considered to be a homogeneous, linear function of its surface and of the distance traveled. Thus dw = f¹(d2) . f2(ds) [4] where dw is the wear of a single ball in time dt, d the diameter of the average ball in ball charge, and ds the distance traveled by the ball in time dt. Indicating that ds - a D n dt, the wear of the average ball in time dt becomes dw = f¹(d2) . f2(Dn dt) 1 --- f¹ (d1) f² (D c3 np-----— dt) \/D = c,d² n, D dt The rate of wear of the average ball is given by dw/dt. dw/dt = c, d² np D lb per hr [5] The weight of the ball charge per unit of mill length is a function of D The number of balls of size d in the ball charge is = f³(D2)/f4(d³). The rate of wear of the total ball charge equals the number of balls times rate of wear of the average ball. Thus rate of total ball wear = — . (dw/dt) w. c, . (l/d) . n,, D lb per hr [6] which is the equation of ball wear in low speed mills. In a mill running at a low speed, grinding is the result of rubbing action within the ball mass and between the ball mass and mill liners. When the speed of the mill is gradually increased toward the critical, the impacting effect of freely falling balls becomes increasingly prominent in comparison with the rubbing action. Reduction of ore takes place partly by rubbing, partly by impact. The share of the freely falling balls in the reduction of ore reaches its practical maximum at a speed somewhat less than the critical; at that speed grinding by rubbing has decreased to a low value. It may be reasonable to think that size reduction by freely falling balls should reach its theoretical maximum at the critical speed, if the fall of the balls were not hindered by the shell of the mill beyond the top point; grinding by rubbing would cease at the critical speed. As a first approximation, wear of freely falling balls may be considered to be a homogeneous, linear function of the force at which they strike pieces of rock and other balls at the toe of the ball charge. The force equals mass times acceleration. The mass of a ball is a function of d3 and its acceleration is a function of the peripheral speed of the mill. The wear of a single ball of size d representing the average ball in a ball charge will therefore be w¹ = f3(F) = f (d3) f7 (v). [7] Indicating that v = D n, and n = c³ np 1/vD, Eq. 7 becomes W1 = cn d3 np Do.5 lb per hr. [8] Total wear of the ball charge equals number of balls times the wear of the average ball. Number of

Jan 1, 1955

By Leonard Logan

The petroleum industry is not peculiar in that it has a problem of stabilization. Economic conditions, not only in the United States but throughout the entire world, are unstable. However, the petroleum industry together with coal mining and agriculture has experienced a longer period of depression than most of the others. It is significant to note that industries engaged in the production of basic raw materials, the primary industries, have not enjoyed as much prosperity since the war as the secondary industries, or those engaged in the fabricating of raw materials and their distribution. The problems of the primary industries are not all the same. Overproduction has existed for several years in agriculture but its causes are not the same as those that have brought about overproduction in the petroleum industry. Unlike agriculture, the institution of property rights and the migratory nature of oil are responsible for the oil man's troubles. Our laws permit the owner of the oil and gas rights, with certain exceptions, to drill when and where he pleases. Since oil is migratory, the adjacent property owner must go and do likewise—drill. This condition spread over a wide area soon brings to the surface more petroleum than can be readily absorbed by the market, creating a condition of overproduction. It is significant to note at this place that when overproduction occurs the complete units in the industry suffer least. A complete unit is taken here to mean a corporation engaged in all the phases of the industry through production, transportation, refining and marketing. In the present depression the complete units in the industry are not in as bad financial condition as those engaged in single phases of the industry. The same thing can be said of the zinc industry, the lumber industry, and the other industries where there are organizations engaged in all the steps through the production of raw materials to the marketing of the finished product. The reason for this is that the complete units are in better position to coordinate all the factors that would work for a stabilized condition than are the units that are engaged in a single branch of the industry.

Jan 1, 1931

By Norris Johnston, Carrol M. Beeson

For many years the permeability of reservoir sands has been measured by flowing air through a cleaned and dried core sample. This differs from the true reservoir permeability in one important respect: the rock particles in the reservoir are surrounded by interstitial water, not air, and their physical shape and condition of hydration are greatly dependent thereon. Permeability as defined must be measured with a single-phase fluid. Since no means exist for removing the oil and gas from a core sample by simply flowing water through it, the sample must be cleaned and then resatu-rated with water before testing. The present discussion attempts to show that after the cleaning process a considerably different permeability is determined with salt or fresh water than is obtained with air. The postulate is made that the salt-water permeability is probably closer to the true reservoir permeability than is the measurement with air. This is discussed in relation to both physically possible and economically feasible measuremerits. Data On more than 1200 core samples are given to show the nature of the effects observed, and a plea is made for others to consider water permeability measurements as a routine necessity, eventually replacing air permeability in regions where the differences are great. Introduction Permeability is defined1 as a "a measure of the capacity of a porous medium to transmit fluids, when there is no interaction between the solids and the fluid." Darcy's law of liquid flow in porous media states: kA?P QµL/A?L [I] where Q represents milliliters of liquid of viscosity p centipoises passed per second through a porous medium of permeability k darcys and cross-sectional area A sq. cm. under a pressure gradient ?P/L atmospheres per centimeter, the flow being understood to be laminar or viscous, not turbulent. This equation defines the darcy. For the case of radial flow in a uniform sand, such as usually exists in the neighborhood of a well in an oil or gas sand, Darcy's law becomes:2 Here h is the net sand thickness in feet, Pe and Pw are pressures at the drainage radius4 and well radius, and re and rw are these radii, respectively. The productivity index3 is defined as the barrels of liquid produced per day per pound per square inch mean pressure differential between ferences and well bore, and is thus: By further definition, the specific productivity index is: or in terms of practical units, and allowing for shrinkage:

Jan 1, 1945

CONTENTS PAGE Rae, Colin C.-A Possible Origin of Oil. Discussed by S. Linker, Colin C. Rae... 2 Cottingham, Kenneth.-Subsurface Conditions on Portion of Arches Fork Anticline. Discussed by David B. Reger 6 Moyer, W. Irwin.-Time to Pay Out as a Basis for Valuation of Oil Properties. Discussed by H. J. Smith 9 Pogue, Joseph E.-Future Demands on Oil Industry of United States. Discussed by James O. Lewis 11 J. J. Walsh.-Coa-lmine Ventilation. Discussed by W. B. Daly, J. J. Walsh, R. R. Sayers, H. H. Stock, George S. Rice, James W. Paul, D. Harrington, T. D. Thomas 15 Longyear, Robert Davis.-Diamond-drill Sampling Methods. Discussed by Ira B. Joralemon, J. J. Rutledge, E. C. Harder 19 Joralemon, Ira B.-Sampling and Estimating Disseminated Copper Deposits. Discussed by J. Parke Channing, John E. Hodge, E.E. Hunner, B. B. Gottsberger, W. Y. Westervelt, W. O. Hotchkiss 20 Boericke, W. F.-Sampling and Estimating Zinc and Lead Orebodies in Mississippi Valley. Discussed by J. Parke Channing, Arthur Thacher 24 Daly, W. B. and Linforth, F. A.-Organization of Mine Sampling at Anaconda. Discussed by George A. Packard, W. B. Daly, B. B. Gottsberger 25 Norris, E. M. and Rahilly, H. J.-Mine Fires. Discussed by R. Dawson Hall, W. B. Daly, Frank Haas, D. Harrington, Robert E. Tally 26 Raymond, R. M.-Safety Practice for Hoisting Ropes. Discussed by B. F. Tillson, Graham Bright, Rudolph Kudlich, J. F. Howe, Robert Peele, H. G. Davis. 30 Howe, J. F.-Use of Wire Rope in Mining Operations. Discussed by Horace F. Lunt, J. F. Howe, B. F. Tillson 36 Tanner, W. N., and Jaccard, F. C.-Wire Rope and Safety in Hoisting at Butte Mines. Discussed by Horace F. Lunt, W. B. Daly, C. L. Colburn, William Kelly, Robert Peele, B. F. Tillson, Graham Bright, Charles E. Locke 38 Richardson, A. S.-Ventilation of Butte Mines of Anaconda Copper Mining Co. Discussed by D. Harrington, Chas. A. Mitke 42 Stuart, Charles E.-Storage-battery Locomotive as Applied to Mine Haulage. Discussed by Howard N. Eavenson, Charles E. Stuart, William Kelly, Arthur Thacher, W. H. Patton, Graham Bright 45 Woodward, C. D.-Electric Haulage Systems in Butte Mines. Discussed by William Kelly, Graham Bright, Howard N. Eavenson, C. E. Arnold, Gerard B. Rosenblatt, K. A. Pauly 47 Harrington, D.-Efficient Ventilation of Metal Mines. Discussed by R. E. Simpson 52 Otagawa, Masayuki.-Mining Methods at the Ashio Copper Mine. Discussed by Horace V. Winchell, D. W. Brunton 52 Stoek, H. H. and Clagett, Thomas H.-Coal Mining Methods. Discussed by P. D. Browning, G. L. Cox, Erskine Ramsay, Frank Haas, George S. Rice.

Jan 6, 1922

By V. Kondic, W. M. Rumball

HUNT and Jackson' have recently suggested that binary eutectics might be classified according to the entropy of fusion of the component phases. Such a classification was in fact proposed2 some time ago by the authors and the purpose of this communication is to present some supporting evidence. As pointed out by Hunt and Jackson' typical metals of low entropy of fusion, ?S, tend to form normal eutectics (using Scheil's terminology3). Where one phase is metallic (low ?S) and the other nonmetallic (high AS) then anomalous structures are formed. These anomalous structures may either be regular (e.g., Bi-Sn)or irregular (e.g., A1-Si). Finally Hunt and Jackson suggest that where both phases are of high ?S regular faceted structures are formed. In the proposed classification2 the ratio of the entropies of fusion is taken as the quantitative parameter, i.e., ?Sa/?SB = E, where e > 1.0. An extensive literature survey has been carried out2,4 for reliable photomicrographs of eutectic structures. The structures, numbering 151, have been classified into two classes, viz., normal (i.e., lamellar and rodlike) and anomalous. The latter group has been arbitrarily subdivided into regular and irregular anomalous eutectics. Details and sources of the structures are given elsewhere.2,4 In the absence of better thermodynamic data the value of E has been determined for each of the systems making the following assumptions and approximations: l) The entropy of fusion of solid solutions may be calculated additively;5 ii) Inter metallic compounds are treated similarly but with the addition of the following term for fully ordered structures.5 -4.573(Ni lOg10 Nl + N2 log10 N2) where Nl and N2 are the atomic fractions. It might be argued that the entropies of fusion are meaningless as the eutectic phases form at some temperature (T,°K) below their true melting point (Ta or Tb). As AS, = Lo/To if La the latent heat of fusion of a, is assumed independent of temperature, the actual entropy change AS& is given by La/Te. The ratio of entropies of fusion then becomes Fig. 1 shows E' plotted against cumulative totals for normal and anomalous systems from which it is seen that normal eutectics predominate at low values of E'; e.g., some 90 pct of normal systems lie below E' = 1.5 with 65 pct of anomalous systems above this value. Fig. 1 also shows that the regular anomalous structures occur mostly at low values of c' possibly suggesting growth more akin to normal than anomalous growth. The choice of c as a classification parameter was based on nucleation concepts, it being observed that metals widely separated in Sundquist and Mondolfo's8 nucleation series were anomalous and those close together normal. The basis of these classification views is really outside the intended scope of this communication but it is hoped to explain them fully in the near future.7 Having arrived at this entropy of fusion classification by nucleation considerations it is interesting to note that Hunt and Jackson's ideas are based on growth considerations. Elsewhere one of the authors4 has shown that an even better classification of the metallographic structures reviewed is obtained from purely conventional heterogeneous nucleation concepts. It has been found that systems having a value of the parameter +b less than 0.28 are almost certainly normal and above this anomalous: V, is the gram atomic volume. This parameter is nevertheless closely related to c and c', these being an approximation of p. The parameter is also related to the other classification3,8,9 which have met with any success in the past. All these classifications are to be reviewed shortly by the authorsU7 A significant thing about the classifications based on

Jan 1, 1968

By AIME AIME

ONE hundred and eighty-three A.I.M.E. members, W. S. Morris with an excellent technical program, John Suman, "oil" President of the Institute, and a Texas norther blew into Dallas for the fall meeting of the Petroleum Division at the Adolphus Hotel, Oct. 16-18. and the most successful result will give future meeting committees a high mark to equal. People were still talking of the terrific heat the week before and it was quite noticeable that with the lowered temperatures, the members were in fine fettle for the technical sessions. The total attendance on Friday noon was

Jan 1, 1941

By E. R. Brownscombe, Francis Collins

The pressure distribution in a reservoir producing an incompressible fluid by radial flow in a horizontal structure is a simple logarithmic function' used daily by reservoir engineers. The assumption of an incompressible liquid is equivalent to assuming that pressure is maintained constant at the well radius and at some external "radius of drainage," or, in other words, that the entire flow into the well passes across the external radius. In most cases a well is surrounded by other wells draining adjoining areas so that the "radius of drainage" is not a line of constant pressure with flow equal to the flow into the well but rather a contour of zero pressure gradient across which no flow occurs, production being due to the expansion of the liquid within the area. The radial flow steady state pressure distribution for this case does not seem to be extensively used despite the fact that the mathematical analysis has been given in detail' and the results are simple and generally applicable. 'The object of this discussion is to develop this result from a physical rather than a mathematical viewpoint, thereby aiding intuition in judging circumstances to which it may be applicable. If the production rate at a well in an unsaturated reservoir is maintained constant while no flow occurs across the outer radius a steady state will soon be reached in which the flow rate or pressure gradient is constant with time at all points in the reservoir. To preserve such a condition it is necessary that the pressure decline at the same rate at all points in the reservoir, that is, the curves of pressure versus radial distance at successive times are all parallel. Then each unit volume of oil is expanding at the same rate and contributing an equal share to the production. The rate of flow q across any circle r is thus proportional to the volume of the reservoir between r and the external radius re, or q = qw (I-r2/r2e) ......(1) where q, is the production from the well and it is assumed that rw is very small compared with re. This equation can be combined with the differential form of Darcy's law for radial flow, 2phkr dp q =—— ........(2) aµß dr ( where q is not a constant as in the incompressible flow case but is a function of r given by Equation (1). If Equation (1) is substituted in Equation (2) the variables p and r can be separated and the result integrated to obtain the pressure distribution p = pw +--------In------------- 2pkh[ rw 2re2] ......(3) This equation differs from the incompressible case only in the addition of the term proportional to the square of the radius

Jan 1, 1950

By O. B. Bennett

WHEN diamond drilling was introduced in the Rhokana mines in 1939 it was used principally for pillar removal and for completion of the upper portions of shrinkage stopes which were being affected by increasing pressure. This method of drilling long blastholes proved so successful that it was extended gradually to cover stoping, pillar recovery, and hanging cave work. BY 1949 virtually all the ~roduction of Mindola and Nkana was being obtained by this method. At the present time 87,500 ft are drilled each month by the 80 diamond drills in daily operation. Responsibility for control and issue of diamond drilling equipment and crowns, as well as tabulation of all performance figures, was taken over by a sPecially formed Roto drill department, which also investigated the problems encountered with this new method. To assist this department a fully equipped test chamber, Fig. 1, was established underground where performances of various types of machines and equipment could be studied under conditions as nearly uniform as possible. Since the establishment of this department, which was eventually taken over and incorporated into the study department, considerable experimental work has been done on every aspect of the subject. The problems can be classified broadly under four headings: improvement of drilling equipment, crown design, machines, and stoping layouts. One of the major problems with drilling equipment has been to eliminate vibration. Owing to flexing of rods in the hole, severe friction is set up on the back end of the 'Ore barrel and On any high spots in the rods, inducing harmonic vibration in the string of rods and causing the crown to chatter against the face. This not only causes premature crown failure but also reduces penetration speeds and increases wear on the machines and rods used. In the early days, when only holes of EX size were drilled, vibration was largely overcome by periodic greasing of rods and core barrel during each run, but with the change-over to the larger BX hole it became obvious that application of grease by hand was inefficient and time-consuming, and attempts were made to perfect a self-lubricating core barrel. A series of these core barrels was made up and tested and a number of the latest type were used under normal operating conditions, but although footages up to 120 ft were drilled without refilling the overall performance was inconsistent, and the idea was shelved in view of the success of the stabilizer rods referred to later in this paper. At the same time tests were made with barrels 5 ft and later 6 ft long instead of the normal 2 ft. Although a slight improvement was noticed, greasing was still necessary. It was found that rod vibration increased as the core barrel became worn, and in an early test chamber experiment crowns drilled with a worn core barrel averaged 95 ft with a diamond loss of 4.76 carats, whereas the same type of crowns with a new barrel averaged 228 ft with a diamond loss of 3.13 carats. until then all BX drilling had been done with B-sized rods, but during a test on a string of BX-sized rods it was noticed that vibration was negligible. Because of the larger surface area of metal bearing on the sides of the hole, however, the friction and resistance of rods of this size rendered them impracticable on any but the most powerful of the machines, The use of stabilizers spaced evenly along the rods was the next logical step, and for this B couplings, see Fig. 2, were set with three tungsten carbide inserts 1 in. long placed around the periphery equidistantly and at an angle of 45" with a right hand lead. These were placed immediately behind the core barrel and then at 12-ft intervals, as it was found that vibration still occurred when the stabilizers were more than 15 ft apart. The effect of these stabilizers was immediately noticeable; holes were drilled with a minimum of vibration, penetration speeds were improved, and as it was no longer necessary to grease the rods there was a marked decrease in the overall drilling time for each hole. While tests were being made with the stabilizer comeb periodic were taking place with a set of tapered threaded rods, and because there was marked improvement in efficiency it was decided to incorporate the stabilizers and tapered threading in all new rods ordered for Rhokana. The feature of these rods is that only four full turns are required to tighten the coupling as against nine for the present type of B rods. Also, as they are self-centering it is virtually impossible to crossthread them. Each rod has a male 5" tapered Acme thread, Fig, 3, on one end and a female at the other, so that separate couplings are unnecessary, and every fifth rod has an

Jan 1, 1955

By R. K. Datta

Eluropium -activated yttrium vanadate, excited by short- and long-wavelength ultraviolet radiations, shows enzission lines near 6100A, the principal ones correspondirzg to transitions of EU+3 ions from 5Do to the F2 energy level. The ~neclmlallistns of absorption and etnissiorz of this phosphor have been empirically studied. The absorption is caused by two separate processes in the matrix. The phosphor YVO4:Eu and tlie matrix YVO, haue essentially the same resectance spectra in the region 2500 to 4000if. There are two broat ah~o?~ption bands: natnely, around 2600 and 3600A regions. Whet? compared with the reflectance spectra of the constituent oxides, namely, Y2O3, V205, Eu2 03, the absorption bands of the tnatvix and the phosphor in the short- and long-wavelength ultraviolet regions can be interpreted as due to charge-transfer processes involving i) Y-O and ii) 17-0, respecti~~ely. The excitation spectrum' of the phosphor has two broad bands with peaks at about 2600 and 3600A regions. U can be postulated that enevgy absorbed under short- crud long-wavelength ultraziolet excitatzon, respectzcely, by Y-0 and V-O parts of the niatrix is transferred by radcatio~zless process to EU+3 ions. Thzs postulate can empirically be proved on the basis of the spectra of the systems (YVO4,-YPO4,):Eu. PO? ~ons do not have' any appreciable absorption in the short or long uv regions. When P0't3 ions are substitlited for v0i3 ions in YVO,:Eu phosphors, the absorption and excitation in the lo~zg uv region are gradually reduced. Ailoreover, the £«+3 emission under 3650A excitation is decreased zuitlz increase in PO^ content, lt~lzereas the emission under 253711 excitation remains esserztially constant with as IILUCIL as 60 mole pct of YPO, in YVO,:En. EUROPIUM-activated yttrium vanadate (YV04:Eu) is a well-known phosptor.'-3 When excited by cathode rays, 2537, or 3650A radiations, YV04:Eu emits typical narrow-band spectrum of EU'3 fluorescence in the region of 5900 to 7100A, a very strong maximum occurring at about 6190A. This emission is considered to be due to 5Do — 7F2 transition of excite: EU*3 in 4f state. Moreover, the emission under 3650A excitation increases with temperature markedly. Because of these properties, YV04:Eu phosphor finds wide application in industries, namely, in color television tube, laser, and high-pressure mercury-vapor lamps. It is the purpose of this paper 1) to present the empirical study of the mechanism of absorption and excitation of YV04:Eu phosphor by ultraviolet radiation, and 2) to offer an explanation for the process of emission. It should be mentioned that a theoretical discussion on the mechanism of absorption in terms of the crystal or ligand field theory is beyond the scope of this paper. Empirical studies presented here are based primarily on spectroscopic and crystal-chemical investigations. EXPERIMENTAL i) Preparation of Materials. The synthesis of vanadate phosphorinvolves preparation of (Yi-.tEuj^Oj, blending the mixed oxide with an oxidic compound of vanadium, such as V205 or NH4V03, and firing the mixture at about 1000°C for several hours when YVO4:Eu forms as a primary phase. (Y1-xEux)203 compositions are prepared by coprecipitation of oxalates, and igniting them at about 1000°C. The vanadium compound is added in excess of the stoichiometric proportion for fluxing purposes. The charge is cooled, ground, and the excess of vanadium is removed by a hot wash (-80°C) of alkali or ammonia. Y(VP)04:Eu samples are prepared by mixing (Yi-xEux)203 with stoichio-metric proportions of (NH4)2HP04 and the vanadium compound. The mixtures are prefired at 700" to 800°C for 1 or 2 hr, then ground and refired at 1150°C. The firings of the phosphors are done in silica crucibles, and the homogeneity of the final products checked by X-ray diffraction analysis. ii) Spectroscopic Measurements. Diffuse reflectance sqectra of the samples within the range 2500 to 7000A are obtained by using CaF2 as standard in Cary Recording Spectrophotometer, Model No. 14. The emission spectra from phosphor plaques, excited under different ultraviolet sources, are obtained by a direct-recording spectroradiometer4 adapted with a grating monochromator with nearly constant dispersion. Maximym sensitivity in the spectral region from 2500 to 7000A is obtained with a quartz-windowed, S-20 response p$otomultiplier. The total' band pass is kept about 30A. The spectra are calibrated against the light from a standard tungsten filament lamp reflected from a magnesium-oxide plaque. Brightness data given throughout this report $re measured from the height of the main peak (6190A) of the emission spectra. The excitation spectra are measured using sodium salicy-late as standard. RESULTS AND DISCUSSION The diffuse reflectance spectra of both pure and activated YV04, along with their constituent components, are shown in Fig. 1. YVO4 shows two broad absorption bands, namely, around 2500 and 3600A, respectively. Since there is little difference between the reflectance spectraoof YVO4 and YVO,:Eu in the uv region (2500 to 4000A), it can be postulated that excitation of the phosphor is mainly due to absorption by the matrix, i.e., YVO4. The question, now, is whether the matrix (Yv04) is excited as a whole, or different components are responsible for the two absorption bands. The characteristic absorption spectra of molecular ions involving transition metal ions, both in aqueous solutions and in crystals, are due to electronic transi-

Jan 1, 1968

By Akinobu Kasami, Keiji Maeda, Makoto Naito, Masaharu Toyama

Gap electroluminescent diodes have been prepared by the vapor phase diffusion of zinc into n-Gap crystals which were grown from a gallium solution (10 wt pct Gap) doped with tellurium and Ga203. A marked improvement in the efficiency of the red electrolumines -cence has been achieved by heat treatment after diffusion. External quantum efficiencies of diodes annealed under optimum conditions are 0.2 to 0.6 pct at room temperature, or about 200 times higher than the efficiencies of diodes quenched after diffusion. The optimum dopant concentrations in the gallium melt from which the crystals were grown are 3to6 x at. pct Te and 4 to 8 x 10-2 mol pct Ga203. The efficient diodes are characterized by linearly graded junctions with an i-layer 0.1 to 0.2u thick. Annealing increases the emission intensity by a factor of 20 to 50 and decreases the current density to 1/3 to 1/8 that of quenched diodes at a given bias. The decrease in current is attributed to an annihilation of deep recombination centers in the depletion layer. The increase in emission intensity is interpreted in terms of an increase in lifetime of minority carriers and an increase in the relative intensity of red-to-infrared emission. The dependence of these quantities on the tellurium and oxygen doping levels is also discussed. A number of studies have been made of the red light emission from for ward-biased Gap diodes.' At room temperature this emission band is centered at 7OOO? with a spectral width of nearly 1000?. Low-tempera-ture photoluminescence indicates that this emission is due to either the radiative annihilation of an exciton bound to a pair of zinc and oxygen atoms substituting on nearest neighbor lattice sites2,3 or the radiative recombination of an electron bound to this Zn-O pair with a hole bound to an isolated zinc shallow acceptor.3 An emission band is also observed with a spectral peak at 9800?. This infrared emission has been shown to be due to the recombination of an electron trapped at an isolated oxygen deep donor with a hole trapped at an isolated zinc acceptor.4 The red emission from Gap diodes is fairly efficient at room temperature because the nearest neighbor Zn-0 pair forms a deep electron trap at 0.3 to 0.4 ev below the edge of the conduction band.2'4 In diodes grown by liquid epitaxy an external quantum efficiency of 2.1 x 10-2 (photon/electron) has been attained by heat treatment at relatively low temperatures.5 This heat treatment was found to increase the efficiency by a factor of 3 to 6. However, no detailed studies have-been reported on the effects of heat treatment. We can only cite Onton and Lorenz's work6 on the change ; in the relative intensity of red-to-infrared emission. Heat treatment has also been tried on junctions built in during growth, but contrary to expectations the efficiency decreased. In-diffusion is a simple and controllable method of fabricating p-n junctions. For Gap, zinc is generally used to form a p-type layer on n-type crystals. The emission efficiencies of in-diffused diodes are, however, extremely low in comparison with liquid epitaxial diodes.' Although efficiencies as high as 2 x 1O-3 have been reported, values from 10-6 to 10-4 are generally obtained by typical diffusion techniques. Out-diffused diodes are known to be a little more efficient than in-diffused diodes. Nevertheless, the quantum efficiency is at most 7 x 10- 3 and ordinarily of the order of 10-4.8 NO results have been reported on heat treatment of either in-diffused or out-diffused diodes. This paper reports a marked improvement in the efficiency of the red emission observed for in-dif-fused diodes as a result of heat treatment after diffusion. The method described reproducibly yields diodes with external quantum efficiencies of 2 to 6 x 10-3. The observed dependence of efficiency on annealing time and on doping level will be discussed in terms of the lifetime of minority carriers and the formation of Zn-O complex pairs. EXPERIMENTAL A) Diode Fabrication. The n-Gap crystals used in this study were grown from a saturated gallium solution by a slow cooling method.8 The Gap content in the gallium melt was fixed to 10 wt pct corresponding to a growth temperature of about 1100 Tellurium was chosen as the n-type dopant and added to the melt in concentrations ranging from 0.001 to 0.06 at. pct. Oxygen was added in the form of Ga2O3, whose concentration was varied from 0.004 to 0.2 mol pct. The resulting crystals were platelets with well-developed (111) surfaces. Typical electrical properties were Hall mobilities of 130 to 30 sq cm per v-sec and carrier concentrations of 1016 to 10" cm-3 at room temperature. Diodes prepared from crystals with relatively low doping levels, in which u = 130 to 100 sq cm per v-sec and n = 0.6 to 6 x 1017 Cm-3, were examined in detail. The p-n junctions were produced in these n-Gap crystals by the diffusion of zinc from the vapor phase by the following procedure. The platelets were carefully lapped on both sides to a thickness of 150 to 200 u while maintaining the (111) orientation. After being etched in hot aqua regia, the crystals together with the zinc were sealed in an evacuated 12 mm ID quartz ampoule 20 cm long. The crystals and the zinc were then separated from each other at opposite ends

Jan 1, 1970

By L. K. Oliver, Marshall

The use of model studies for the development of invasion patterns for cycling is .illustrated by model studies obtained with a recently developed apparatus in the solution of actual cycling problems. Introduction Depletion of a gas reservoir by cycling under pressure maintenance may be divided into three general phases. In the first phase, injection of dry gas is used to move all possible wet gas to producing wells prior to breakthrough of appreciable quantities of dry gas into producing wells. In the second phase, injection moves additional wet gas to producing wells while moderate quantities of dry gas are being produced. The third phase consists of production without injection to deplete the commercial gas reserve which remains after the cycling operation. Thus, in the first phase, a portion of the reservoir is invaded by dry gas, and the dry gas usually displaces something less than 100 pct of the wet gas from the invaded portions of the reservoir. The second phase enlarges the invaded portion of the reservoir and, at the same time, increases recovery from that zone invaded by dry gas in the first phase of the cycling operation. The result is an early yield of a substantial quantity of the liquefiable hydrocarbons in the reservoir with a minimum of the retrograde losses which occur in some reservoirs. The overall recovery from such an operation is usually high. The summation of the paths taken by dry gas in a cycling operation can be termed an invasion pattern. The use of electrical models to predict invasion patterns has been the subject of several contributions to the literature.1-3 The results of such model studies as applied to actual cases has been discussed by Kelton4 and Miller and Lents.= Recently, an improved apparatus for conducting potentiometric model studies has been developed, as described by Lee.V he purpose of this paper is to present model studies or invasion patterns obtained with this instrument in the solution of actual cycling problems. The percentage of displacement of wet gas within the invaded portion of the reservoir in cycling, increase in recoveries of wet gas by continuing cycling after dry gas breakthrough, recoveries of wet and dry gas by production after cycling, or economic factors in cycling are beyond the scope of this paper. Discussions which follow will be limited entirely to the development of suitable invasion patterns for cycling under pressure maintenance and the use of model studies therein. Discussion OF Results In using model studies to predict invasion patterns in cycling, some factors which influence the results are the following:

Jan 1, 1948

By Marshall, L. K. Oliver

The use of model studies for the development of invasion patterns for cycling is .illustrated by model studies obtained with a recently developed apparatus in the solution of actual cycling problems. Introduction Depletion of a gas reservoir by cycling under pressure maintenance may be divided into three general phases. In the first phase, injection of dry gas is used to move all possible wet gas to producing wells prior to breakthrough of appreciable quantities of dry gas into producing wells. In the second phase, injection moves additional wet gas to producing wells while moderate quantities of dry gas are being produced. The third phase consists of production without injection to deplete the commercial gas reserve which remains after the cycling operation. Thus, in the first phase, a portion of the reservoir is invaded by dry gas, and the dry gas usually displaces something less than 100 pct of the wet gas from the invaded portions of the reservoir. The second phase enlarges the invaded portion of the reservoir and, at the same time, increases recovery from that zone invaded by dry gas in the first phase of the cycling operation. The result is an early yield of a substantial quantity of the liquefiable hydrocarbons in the reservoir with a minimum of the retrograde losses which occur in some reservoirs. The overall recovery from such an operation is usually high. The summation of the paths taken by dry gas in a cycling operation can be termed an invasion pattern. The use of electrical models to predict invasion patterns has been the subject of several contributions to the literature.1-3 The results of such model studies as applied to actual cases has been discussed by Kelton4 and Miller and Lents.= Recently, an improved apparatus for conducting potentiometric model studies has been developed, as described by Lee.V he purpose of this paper is to present model studies or invasion patterns obtained with this instrument in the solution of actual cycling problems. The percentage of displacement of wet gas within the invaded portion of the reservoir in cycling, increase in recoveries of wet gas by continuing cycling after dry gas breakthrough, recoveries of wet and dry gas by production after cycling, or economic factors in cycling are beyond the scope of this paper. Discussions which follow will be limited entirely to the development of suitable invasion patterns for cycling under pressure maintenance and the use of model studies therein. Discussion OF Results In using model studies to predict invasion patterns in cycling, some factors which influence the results are the following:

Jan 1, 1948

By J. R. Kyte, R. L. Dalton, V. O. Naumann, R. L. Ridings, R. W. Greene

This paper presents a one-dimensional numerical method for calculating dissolved-gas-drive behavior for a single well or a linear reservoir. Pressure and saturation distributions can be calculated, including the effects of capillary and gravity forces. The analysis has been programmed for solution on the IBM 7090 digital computer. A comparison of experimental and calculated behavior for two linear models demonstrates that the method is suitable for calculating dissolved-gas-drive behavior under reservoir conditions of flow. Dissolved-gas-drive tests were run, at different production rates and with oils of different viscosities, on short (6.ft) and long (173ft) flow models. For tests approximating reservoir pressure gradients and flow rates, there was excellent agreement between experimental and calculated results. A series of calculations of well behavior for thin, horizontal, homogeneous, dissolved-gas-drive reservoirs shows that ultimate recovery is independent of production rate or well spacing in such cases. These calculations also show that Muskat's method and similar material-balance analyses are not applicable under some conditions particularly for high pressure drawdowns. INTRODUCTION The problem of calculating dissolved-gas-drive reservoir performance has received a great deal of attention throughout the oil-producing indusfry for many years. Really significant advances, however, have been made only in recent years. The rapid evolution of high-speed computing equipment and techniques has opened up new approaches to the problem and led to realistic, quantitative analyses free of many of the assumptions and limitations of earlier methods. The one-dimensional numerical method described in this paper includes the effects of both gravity and capillary forces. A number of test calculations, based on different rates, spacings, and rock and fluid properties, have shown that the method is adequate for systems that can be reasonably represented by a one-dimensional model (linear or radial) and in which fluid segregation perpendicular to the direction of flow is not important. Along with the development of mathematical methods, an experimental program was conducted and the data were used to test the validity of the theoretical basis of the mathematical method. Linear models were used and all experiments were run using 1,000-psig bubble-point oils. The use of long, high-pressure models enabled us to more closely approach reservoir gradients and flow rates. MATHEMATICAL FORMULATION DIFFERENTIAL EQUATIONS The differential equations describing dissolved-gas-drive behavior in one dimension dare summarized here. They include Darcy's law for flow of oil and gas (Eqs. 1 and 2) and the equations for conservation of mass for oil and gas (Eqs. 3 and 4). The oil and gas pressures are related by capillary pressure (Eq. 51.